U.S. Pat. No. 4,719,615, owned by applicants' assignee, discloses an erasable bump-forming medium having a dual layer recording structure of two thermally and mechanically active layers which are bonded together and cooperate to write, retain, and erase data in the medium. The layers are optically coupled, having substantially similar indices of refraction. The medium is adapted to be inscribed and erased by lasers in a non-vesicular, non-ablative technique. The medium as disclosed forms an air-incident bump toward the laser source.
A number of other patents including Cornet U.S. Pat. No. 4,398,203, Mayer et al. U.S. Pat. No. 4,584,259, Maffit U.S. Pat. No. 4,430,659, Bell U.S. Pat. No. 4,300,227, and Howe et al. U.S. Pat. No. 4,336,545 disclose optical data storage media which use a relatively thick, highly reflective layer beneath the data layer(s).
Ahn et al. U.S. Pat. No. 4,578,788 discloses a non-erasable medium including an embedded servo track with a thin film having a high optical index of refraction on the servo track. The thin, high-index film is partially reflective. Data is recorded in the medium with a non-erasable, vesicular technique by heating a metal data layer until an adjacent organic layer gasifies and causes the data layer to form a vesicle.